Process for the rolling of bar of alloy tool steel for wood chisels

Abstract

The present application belongs to the field of rolling technology, and particularly relates to a rolling process of alloy tool steel wire rod for wood chisel. The present application controls heating temperature, heating time and air-fuel ratio, and simultaneously controls the speed of Stelmor roller table and the number of opened holding covers to stabilize the temperature interval of wire rod entering the cover and effectively control the decarburization problem generated in the heating and cooling process of the wire rod. In addition, the final rolling temperature and wire laying temperature are controlled to ensure the full transformation of pearlite structure of the wire rod in the holding cover and avoid the generation of martensite structure in the cooling process. The decarburization depth of the Φ5.5-Φ8.0 mm wire rod rolled by the present application is less than or equal to 0.04 mm, the decarburization of the wire rod with a size greater than 8 mm is less than 0.4D%, and the cross-section microstructure of the wire rod is pearlite.

Description

Technical Field

[0001] This invention belongs to the field of rolling technology and relates to a method for producing alloy tool steel wire rod, specifically a rolling process for alloy tool steel wire rod for woodworking chisels. Background Technology

[0002] Alloy tool steel is a type of steel in which alloying elements such as chromium, nickel, and vanadium are added to carbon tool steel to improve its hardenability, toughness, wear resistance, and heat resistance. Electric woodworking chisels are a type of product with extremely high requirements among alloy tool steels. The finished product must possess high strength, high wear resistance, torsional resistance, and explosion resistance. Because the processed product needs to undergo fatigue, elasticity, and torsional resistance tests, strict requirements are placed on the composition design and mechanical properties.

[0003] The high carbon and silicon content in the chemical composition of alloy tool steel used for woodworking chisels makes the wire rod highly susceptible to decarburization, and the depth of decarburization directly affects the surface hardness of the wire rod and the processed product. Furthermore, the presence of alloying elements such as chromium, nickel, and vanadium makes it difficult to control the uniformity of the microstructure during the rolling process, easily leading to the precipitation of hard and brittle martensite, causing brittle fracture during packaging, transportation, and user processing. Simultaneously, the uneven microstructure of the wire rod directly affects the user's heat treatment process, further increasing downstream processing costs. Summary of the Invention

[0004] The purpose of this invention is to provide a rolling process for alloy tool steel wire rods for woodworking chisels. The wire rods produced by this process have a pearlitic microstructure, which effectively prevents brittle fracture of the wire rods during packaging, transportation and user processing. At the same time, the wire rods are obtained with shallow decarburization, and the various properties of the woodworking chisels are stable after use.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A rolling process for alloy tool steel wire rod for woodworking chisels includes the following steps:

[0007] (1) In the heating process, the total heating time of the billet is 90 to 150 minutes, the temperature of the preheating section is 700 to 800℃, the temperature of the heating section is 900 to 1000℃, the temperature of the soaking section is 1020 to 1080℃, and the soaking section time does not exceed 60 minutes.

[0008] (2) In the rolling process, after the billet exits the furnace, it is descaled by high-pressure water at a pressure of 20-25 MPa. After descaling, there is no iron oxide scale residue. It is rolled by a combination of finishing mill and MINI mill. The rolling temperature is controlled by adjusting the water volume in the water tank. The temperature of entering the finishing mill is 850-910℃, and the temperature of entering the MINI mill is 780-840℃. After being coiled by the wire rod spinning machine, it becomes wire rod.

[0009] (3) In the cooling process, the wire rod spinning temperature is 770-830℃, after spinning, the wire rod is cooled on the Stelmor scattered cooling transport line, then enters the heat preservation cover for heat preservation, the entering temperature is 650-700℃, the exiting temperature is less than 580℃, after exiting the cover, the wire rod is gathered, packed and stored.

[0010] Further, in the step (1), the cross section size of the billet is 160mm x 160mm.

[0011] Further, in the step (1), the air-fuel ratio in the furnace is less than or equal to 0.5 or the residual oxygen content is less than or equal to 2%.

[0012] Further, in the step (2), there are three water tanks before the finishing rolling mill group, two water tanks between the finishing rolling mill and the MINI rolling mill, and two water tanks between the MINI rolling mill and the spinning machine, the rolling temperature is controlled by evenly distributing the water volume of each water tank.

[0013] Further, in the step (3), the Stelmor scattered cooling transport line is 120m long, 24 heat preservation covers are arranged, and 14 groups of roller speeds can be adjusted individually, the 24 heat preservation covers from spinning to gathering are the first to the twenty-fourth, the scattered cooling roller under the first to the tenth heat preservation cover corresponds to the first to the tenth fan respectively, the 14 groups of rollers are numbered from 1# to 14#, and the cooling requirements of the wire rods of different specifications on the Stelmor scattered cooling line are as follows:

[0014] Φ5.5-Φ8.0mm, roller speed 1#-3#: 0.33m / s, 4#-11#: 0.36m / s, 12#: 0.4m / s, 13#: 0.46m / s, 0.53m / s, the first to the fourth heat preservation covers are opened, the remaining heat preservation covers are all closed, and the fans are all closed.

[0015] Φ9.0-Φ12.0mm, roller speed 1#-3#: 0.3m / s, 4#-11#: 0.33m / s, 12#: 0.4m / s, 13#: 0.46m / s, 0.53m / s, the first to the fifth heat preservation covers are opened, the remaining heat preservation covers are all closed, and the fans are all closed.

[0016] Φ13-Φ16.0mm, roller speed 1#-11#: 0.3m / s, 12#: 0.36m / s, 13#: 0.4m / s, 0.46m / s, the first to the sixth heat preservation covers are opened, the remaining heat preservation covers are all closed, and the fans are all closed.

[0017] Φ17.0-Φ20.0mm, roller speed 1#-11#: 0.26m / s, 12#-14#: 0.3m / s, the first to the fifth heat preservation covers are opened, the remaining heat preservation covers are all closed, the first and the second fans are opened, and the air volume is 40% and 30% respectively.

[0018] Φ21.0~Φ25.0mm, roller table speed 1#~11#: 0.24m / s, 12#~14#: 0.3m / s, open the first to the sixth heat preservation cover, the rest of the heat preservation cover is closed, open the first to the third fan, the air volume is 50%, 40%, 40% respectively;

[0019] The chemical composition of the wire rod is in percentage by mass, and the component ratio is C: 0.70~0.76, Si: 1.40~1.60, Mn: 0.50~0.80, P≤0.025, S≤0.020, Cr: 1.00~1.20, Ni: 0.20~0.26, Al: 0.020~0.040, V: 0.14~0.20, and the rest is iron and inevitable impurities.

[0020] The present application controls the heating temperature, heating time and air-fuel ratio in the heating furnace during the heating process of the billet, controls the roller table speed of the Stelmor, the number of open heat preservation covers and the opening of the large-size wire rod fan, stabilizes the wire rod temperature interval in the cover, effectively controls the decarburization problem generated in the heating and cooling process of the wire rod. In addition, by controlling the finish rolling temperature and the wire drawing temperature, the transformation of the pearlite structure in the heat preservation cover is ensured, and the generation of the martensite structure in the cooling process is avoided.

[0021] Compared with the traditional rolling process, the present application has the beneficial effects that: in the rolling process, the cooling water flow of each water tank is evenly distributed to control the temperature at the entrance of the finishing mill, before the MINI mill and at the wire drawing temperature respectively, to prevent abnormal structure generated by local rapid cooling; the wire rod is controlled at low temperature when entering the finishing mill and the MINI mill, to promote the generation of crystal defects in the austenite structure in the large deformation rolling process, to increase the phase change driving force, to shorten the phase change incubation period and to increase the phase change driving force; at the same time, since the length of the Stelmor cooling transportation line is fixed, after the wire rod is drawn, it is necessary to prevent the wire rod from being densely stacked, the temperature of the wire rod entering the cover is high, and the two-phase zone structure transformation decarburization is generated in the heat preservation cover, and it is also necessary to ensure that the wire rod fully completes the structure transformation in the heat preservation cover, to prevent the generation of the martensite structure after rapid cooling due to high temperature. Therefore, the wire rod with a diameter of Φ5.5~Φ16.0mm adjusts the temperature entering the cover by controlling the number of heat preservation covers, and the wire rod with a diameter of Φ17.0~Φ25.0mm adjusts the temperature entering the cover by opening a certain number of fans, to ensure that the wire rod of different specifications can fully perform phase change in the heat preservation cover. The wire rod with a diameter of Φ5.5~Φ8.0mm rolled by the present application has a decarburization depth of less than or equal to 0.04mm, and the wire rod with a diameter greater than 8mm has a decarburization of less than 0.4D%, and the cross-sectional microstructure of the wire rod is pearlite. BRIEF DESCRIPTION OF DRAWINGS

[0022] The content expressed by each drawing of the present application specification is briefly described as follows:

[0023] Figure 1 Microstructure of Φ5.5mm wire rod obtained by using the rolling process of Example 1;

[0024] Figure 2 Microstructure of Φ12.0mm wire rod obtained by using the rolling process of Example 2;

[0025] Figure 3 Microstructure of Φ14.0mm wire rod obtained by using the rolling process of Example 3;

[0026] Figure 4 Microstructure of Φ19.0mm wire rod obtained by using the rolling process of Example 4;

[0027] Figure 5 Microstructure of Φ23.0mm wire rod obtained by using the rolling process of Example 5;

[0028] Figure 6 Microstructure of Φ5.5mm wire rod obtained by using the rolling process of Comparative Example 1;

[0029] Figure 7 Microstructure of Φ12.0mm wire rod obtained by using the rolling process of Comparative Example 2;

[0030] Figure 8 Microstructure of Φ14.0mm wire rod obtained by using the rolling process of Comparative Example 3;

[0031] Figure 9 Microstructure of Φ19.0mm wire rod obtained by using the rolling process of Comparative Example 4;

[0032] Figure 10 Microstructure of Φ23.0mm wire rod obtained by using the rolling process of Comparative Example 5. DETAILED DESCRIPTION

[0033] The following production examples of Φ5.5mm, Φ12.0mm, Φ14.0mm, Φ19.0mm and Φ23.0mm wire rods are further described in detail in connection with the chemical composition of the continuous casting billet having a cross-sectional size of 160mm x 160mm, the component ratio being C: 0.73, Si: 1.50, Mn: 0.65, P: 0.015, S: 0.008, Cr: 1.05, Ni: 0.22, Al: 0.029, V: 0.18, the rest being iron and unavoidable impurities, in terms of mass percentage, wherein the conditions not specified are conventional conditions.

[0034] Example 1

[0035] (1) The billet is heated in a heating furnace for 120 minutes, the preheating section temperature is 750-800°C, the heating section temperature is 900-980°C, the soaking section temperature is 1030-1060°C, the high temperature section time is 40 minutes, and the air-fuel ratio in the heating furnace is 0.45.

[0036] (2) After the billet is discharged, high-pressure water descaling is used, the descaling pressure is 25 MPa, no oxide scale is left after descaling, the temperature is controlled to be 890-910°C by evenly distributing the flow of 3 water tanks before entering the finishing, the temperature is controlled to be 790-810°C by evenly distributing the flow of 2 water tanks before entering the MINI, and Φ5.5 mm wire rod is obtained after being coiled by the wire drawing machine.

[0037] (3) The wire drawing temperature is 775-790°C, the wire rod is cooled on the Stelmor scattered cooling transportation line after wire drawing, the roller speed is 0.33 m / s for 1#-3#, 0.36 m / s for 4#-11#, 0.4 m / s for 12#, 0.46 m / s for 13#, 0.53 m / s, the first to fourth heat preservation covers are opened, and the rest of the heat preservation covers are all closed, and all the fans are closed. The entering cover temperature is 650-690°C, the wire rod is preserved in the heat preservation cover, the out cover temperature is 450-520°C, and the wire rod is gathered, packed and stored after being discharged. The microstructure of the wire rod is pearlite, and the decarburization layer depth is 0.02 mm.

[0038] Example 2

[0039] (1) The billet is heated in a heating furnace for 125 minutes, the preheating section temperature is 700-800°C, the heating section temperature is 900-990°C, the soaking section temperature is 1040-1070°C, the high temperature section time is 50 minutes, and the air-fuel ratio in the heating furnace is 0.45.

[0040] (2) After the billet is discharged, high-pressure water descaling is used, the descaling pressure is 25 MPa, no oxide scale is left after descaling, the temperature is controlled to be 880-910°C by evenly distributing the flow of 3 water tanks before entering the finishing, the temperature is controlled to be 800-820°C by evenly distributing the flow of 2 water tanks before entering the MINI, and Φ12.0 mm wire rod is obtained after being coiled by the wire drawing machine.

[0041] (3) The wire drawing temperature is 780-800°C, the wire rod is cooled on the Stelmor scattered cooling transportation line after wire drawing, the roller speed is 0.3 m / s for 1#-3#, 0.33 m / s for 4#-11#, 0.4 m / s for 12#, 0.46 m / s for 13#, 0.53 m / s, the first to fifth heat preservation covers are opened, and the rest of the heat preservation covers are all closed, and all the fans are closed. The entering cover temperature is 660-695°C, the wire rod is preserved in the heat preservation cover, the out cover temperature is 470-540°C, and the wire rod is gathered, packed and stored after being discharged. The microstructure of the wire rod is pearlite, and the decarburization layer depth is 0.04 mm.

[0042] Example 3

[0043] (1) The billet is heated in a heating furnace for 120 minutes, the preheating section temperature is 700-800°C, the heating section temperature is 920-980°C, the soaking section temperature is 1030-1070°C, the high temperature section time is 55 minutes, and the air-fuel ratio in the heating furnace is 0.45.

[0044] (2) After the billet is discharged, high-pressure water descaling is used, the descaling pressure is 25 MPa, no oxide scale is left after descaling, the temperature is controlled at 870-900°C before entering the finishing by evenly distributing the flow of 3 water tanks, the temperature is controlled at 800-820°C before entering the MINI by evenly distributing the flow of 2 water tanks, and Φ14.0 mm wire rod is obtained after being coiled by the wire drawing machine.

[0045] (3) The wire drawing temperature is 785-810°C, the wire rod is cooled on the Stelmor scattered cooling line after wire drawing, the roller speed is 0.3 m / s at 1#-11#, 0.36 m / s at 12#, 0.4 m / s at 13#, 0.46 m / s, the first to sixth heat preservation covers are opened, the rest of the heat preservation covers are all closed, and all the fans are closed. The cover temperature is 665-690°C, the wire rod is preserved in the heat preservation cover, the cover temperature is 460-560°C, the wire rod is gathered, packed and stored after being discharged. The microstructure of the wire rod is pearlite, and the decarburization layer depth is 0.05 mm.

[0046] Example 4

[0047] (1) The billet is heated in a heating furnace for 140 minutes, the preheating section temperature is 700-800°C, the heating section temperature is 920-980°C, the soaking section temperature is 1050-1075°C, the high temperature section time is 50 minutes, and the air-fuel ratio in the heating furnace is 0.45.

[0048] (2) After the billet is discharged, high-pressure water descaling is used, the descaling pressure is 25 MPa, no oxide scale is left after descaling, the temperature is controlled at 870-905°C before entering the finishing by evenly distributing the flow of 3 water tanks, the temperature is controlled at 805-830°C before entering the MINI by evenly distributing the flow of 2 water tanks, and Φ19.0 mm wire rod is obtained after being coiled by the wire drawing machine.

[0049] (3) The wire drawing temperature is 795-820°C, the wire rod is cooled on the Stelmor scattered cooling line after wire drawing, the roller speed is 0.26 m / s at 1#-11#, 0.3 m / s at 12#-14#, the first to fifth heat preservation covers are opened, the rest of the heat preservation covers are all closed, the first to second fans are opened, and the air volume is 40% and 30% respectively. The cover temperature is 660-680°C, the wire rod is preserved in the heat preservation cover, the cover temperature is 500-570°C, the wire rod is gathered, packed and stored after being discharged. The microstructure of the wire rod is pearlite, and the decarburization layer depth is 0.06 mm.

[0050] Example 5

[0051] (1) Steel billets are heated in a heating furnace for 135 minutes, the preheating temperature is 700-800°C, the heating temperature is 900-1000°C, the soaking temperature is 1040-1080°C, the high temperature time is 50 minutes, and the air-fuel ratio in the heating furnace is 0.45.

[0052] (2) After the steel billets are discharged, high-pressure water is used for descaling, the descaling pressure is 25 MPa, and no iron oxide scale is left after descaling. The temperature is controlled at 890-910°C by averaging the flow of 3 water tanks before entering the finishing, and the temperature is controlled at 810-840°C by averaging the flow of 2 water tanks before entering the MINI. After being coiled by the spinning machine, Φ23.0 mm wire rod is obtained.

[0053] (3) The spinning temperature of the wire rod is 800-830°C, and the wire rod is cooled on the Stelmor scattered cooling line after spinning, the roller speed is 0.24 m / s at 1#-11#, 0.3 m / s at 12#-14#, the first to sixth heat preservation covers are opened, and the remaining heat preservation covers are all closed. The first to third fans are opened, and the air volume is 50%, 40%, and 40% respectively. The entering cover temperature is 660-680°C, the wire rod enters the heat preservation cover for heat preservation, the exiting cover temperature is 520-560°C, and the wire rod is gathered, packaged, and stored after exiting the cover. The microstructure of the wire rod is pearlite, and the decarburization layer depth is 0.07 mm.

[0054] Comparative Example 1

[0055] Comparative Example 1 and Example 1 are compared, and in the cooling of step 3 of Example 1, the first to second fans are opened, and the air volume is set to 20% and 10%. The entering cover temperature is 500-560°C, the wire rod enters the heat preservation cover for heat preservation, and the exiting cover temperature is 400-500°C. The other conditions are the same as those in Example 1. The microstructure of the obtained wire rod is martensite, and the decarburization layer depth is 0.02 mm.

[0056] Comparative Example 2

[0057] Comparative Example 2 and Example 2 are compared, and in step 3 of Example 1, the first to sixth heat preservation covers are opened, and the remaining heat preservation covers are all closed. The heat preservation covers are all opened, and the other conditions are the same as those in Example 2. The microstructure of the obtained wire rod is martensite, and the decarburization layer depth is 0.05 mm.

[0058] Comparative Example 3

[0059] Comparative Example 3 Compared with Example 3, the "roller speed 1#-11#: 0.3 m / s, 12#: 0.36 m / s, 13#: 0.4 m / s, 0.46 m / s, open the first to the sixth heat insulation cover, and the rest of the heat insulation cover is closed, and the fan is closed" in Example 3 step 3 is adjusted to "roller speed 1#-11#: 0.15 m / s, 12#: 0.36 m / s, 13#: 0.4 m / s, 0.46 m / s, open the first heat insulation cover, and the rest of the heat insulation cover is closed, and the fan is closed", the temperature in the cover is 740-780℃, the wire rod is kept in the heat insulation cover, the temperature out of the cover is 490-650℃, and the other conditions are the same as those in Example 3. The microstructure of the wire rod obtained is pearlite, the wire rod test appears a full decarburized layer (the full decarburized layer is not allowed to appear), and the full decarburized layer is 0.02 mm.

[0060] Comparative Example 4

[0061] Comparative Example 4 Compared with Example 4, the "open the first to the second fan, and the air volume is 40% and 30% respectively" in Example 4 step 3 is adjusted to "the fan is closed", the temperature in the cover is 680-730℃, the wire rod is kept in the heat insulation cover, the temperature out of the cover is 540-630℃, and the other conditions are the same as those in Example 4. The microstructure of the wire rod obtained is martensite + a small amount of bainite, and the decarburized layer depth is 0.07 mm.

[0062] Comparative Example 5

[0063] Comparative Example 5 Compared with Example 5, the "open the first to the third fan, and the air volume is 50%, 40% and 40% respectively" in Example 5 step 3 is adjusted to "open the first to the third fan, and the air volume is 80%, 80% and 70% respectively", the temperature in the cover is 570-650℃, the wire rod is kept in the heat insulation cover, the temperature out of the cover is 480-540℃, and the other conditions are the same as those in Example 5. The microstructure of the wire rod obtained is martensite + pearlite, and the decarburized layer depth is 0.06 mm.

[0064] The raw materials and equipment used in the application are the commonly used raw materials and equipment in the field unless otherwise specified; the methods used in the application are the conventional methods in the field unless otherwise specified. The above description is only a better implementation of the application, and is not used to limit the application, and any modification made according to the technical essence of the application to the above examples is included in the protection scope of the application.

Claims

1. A rolling process of an alloy tool steel rod for wood chisel, characterized by, The chemical composition of the wire rod is as follows in terms of mass percentage: 0.70 < C ≤ 0.76, Si: 1.40 ~ 1.60, Mn: 0.50 ~ 0.80, P ≤ 0.025, S ≤ 0.020, Cr: 1.00 ~ 1.20, Ni: 0.20 ~ 0.26, Al: 0.020 ~ 0.040, V: 0.14 ~ 0.20, and the rest is iron and inevitable impurities; the production steps are as follows: (1) in the heating process, the total heating time of the billet is 90 ~ 150 minutes, the preheating temperature is 700 ~ 800℃, the heating temperature is 900 ~ 1000℃, the soaking temperature is 1020 ~ 1080℃, and the soaking time is not more than 60 minutes; (2) in the rolling process, the billet is descaled by high-pressure water after being discharged, the descaling pressure is 20 ~ 25MPa, no iron oxide scale is left after descaling, combined rolling is carried out by using finishing rolling + MINI unit, there are 3 water tanks before the finishing rolling unit, 2 water tanks between the finishing rolling unit and the MINI rolling unit, and 2 water tanks between the MINI rolling unit and the wire rod drawing machine, the rolling temperature is controlled by uniformly distributing the water volume of each water tank; the temperature entering the finishing rolling unit is 850 ~ 910℃, the temperature entering the MINI rolling unit is 780 ~ 840℃, and the wire rod is obtained after being coiled by the wire rod drawing machine; (3) in the cooling process, the wire rod drawing temperature is 770 ~ 830℃, the wire rod is cooled on the Stelmor scattered cooling transportation line after drawing, and then is cooled in the heat preservation cover, the cover entering temperature is 650 ~ 700℃, the cover exiting temperature is less than 580℃, and the wire rod is gathered, packed and stored after exiting the cover.

2. The rolling process of a bar of alloy tool steel for chisels for woodwork according to claim 1, characterized in that: In the step (1), the cross-sectional size of the billet is 160mm x 160mm.

3. The process for rolling of alloy steel wire rod for wood chisel as claimed in claim 1 wherein: In the step (1), the air-fuel ratio in the furnace is ≤0.5 or the residual oxygen content is ≤2%.

4. The process for rolling of alloy steel wire rod for wood chisel as claimed in claim 1 wherein: In the step (3), the Stelmor scattered cooling transportation line is 120m long, 24 heat preservation covers are arranged, and 14 groups of roller speeds can be adjusted individually; the 24 heat preservation covers are the 1st to 24th in sequence from the wire rod drawing to the gathering; the scattered cooling roller under the 1st to 10th heat preservation covers respectively corresponds to the 1st to 10th fans; the 14 groups of roller numbers are 1# to 14# from the wire rod drawing to the gathering; the cooling requirements of different specifications of wire rods on the Stelmor scattered cooling line are as follows: Φ5.5 ~ Φ8.0mm, roller speed 1# ~ 3#: 0.33m / s, 4# ~ 11#: 0.36m / s, 12#: 0.4m / s, 13#: 0.46m / s, 14#: 0.53m / s, the 1st to 4th heat preservation covers are opened, and the rest of the heat preservation covers are all closed, and the fans are all closed; Φ9.0 ~ Φ12.0mm, roller speed 1# ~ 3#: 0.3m / s, 4# ~ 11#: 0.33m / s, 12#: 0.4m / s, 13#: 0.46m / s, 14#: 0.53m / s, the 1st to 5th heat preservation covers are opened, and the rest of the heat preservation covers are all closed, and the fans are all closed; Φ13~Φ16.0mm, roller speed 1#~11#: 0.3m / s, 12#: 0.36m / s, 13#: 0.4m / s, 14#: 0.46m / s, open the first to the sixth heat shield, the rest of the heat shield is closed, the fan is closed; Φ17.0~Φ20.0mm, roller speed 1#~11#: 0.26m / s, 12#~14#: 0.3m / s, open the first to the fifth heat shield, the rest of the heat shield is closed, open the first to the second fan, the air volume is 40%, 30% respectively; Φ21.0~Φ25.0mm, roller speed 1#~11#: 0.24m / s, 12#~14#: 0.3m / s, open the first to the sixth heat shield, the rest of the heat shield is closed, open the first to the third fan, the air volume is 50%, 40%, 40% respectively.

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